This is a critical bug with Document-Based Apps (SwiftData). If you download the WWDC 2023 sample code for"Building a document-based app using SwiftData" , open it in Xcode 16.1, and run it on an iOS 18+ simulator, you'll encounter a major issue. When you exit a document and reopen it, you'll find that the changes you just made were not saved.
iOS 18 has effectively rendered last year's WWDC 2023 sample code obsolete! Has anyone managed to successfully save data in a Document-Based App using SwiftData?